Antenna system and method of using same



Dec. 30, 1947. .l A. G. KANDOIAN 2,433,369

ANTENNA SYSTEM AND METHOD OF' USING SAME INVENTOR ,4RM/6 KA/VD/AN BY m ATTORNEY Dec. 30, 1947.' A. G. KANDOIAN ANTENNAl SYSTEM AND METHOD OF USING SAME 4 Sheets-Sheet 2 Filed July 24, 1942 INVENTOR ATTORN EY Dec. 30, 1947. yA. G. KANDOIAN- ANTENNA SYSTEM AND METHOD OF USING SAME 4 Sheets-Sheet 3 Firled July 24, 1942 To TPA/Gump INVENToR APM/ /(4N0.0//4/Y ATTORNEY Dec. 30, 1947. A. G. KANDIAN ANTENNA SYSTEM AND METHOD OF' USING SAME Filed Jly 24,` 1942 4sheetssneet 4 .NUMSQQ HE/HT '0F HUIZONTAL D/POLE INVENTOR APM/6 G. KN//Y ATTORNEY Patented Dec. 30, 1947 UNITED STATES PATENT OFFICE SYSTEM AND METHOD OF VUSING SAME n I Armg: G. Kandoian, New York, NL..,.-assignor to. Federal Telephonev and Radio Corporation.,v a

corporation of Delaware.

Application July 24, 1942,.seriarNn..452,124-

4n claims. (ci. 25o-.125m

This invention relates to-antenna systems and more particularly' to adjustable antennae and methodv for using same to scan over a range of angles in vertical planes.

In the use of short-wave radio locator equipment using the echo principle for locating appreaching obstacles or craft, particularly aircraft,

itis necessary to provide for scanning a radiation patternV in a vertical direction in order toA determine the altitude of. an, aircraft. Generally, at the same time horizontal scanning of the radiation. pattern is effected to obtain the direction so that upon obtaining the distance` to the craft, its4 position. can. be. precisely located. In such systems considcrablediiliculty isvv encountered with the known types'otequipment. in ascertaining precisely thefelevation,v angle of an aircraft. This difficultyV is encountered. because. at low angles the tilting of ya. directive antenna will. notY be effective to indicate the altitude.

It is an object of my invention to overcomer the aforesaid difficulty of verticalfanglescanning and, in accordance, with my invention, I accomplish it by providing anV antennav adjustable in height` above the surface of. the earth and utilize the radiation lobes developed` when the antenna is raised or 1owered-, .as the case` may be', to locate the position of a-n aircraft in the vertical angle. This may be-` accomplished by' adjusting the elevationall position oi" the antenna until. the lrst maximum. indication-is reached, or iti may be accomplished by adjustment ofi the antenna unit until` the minimum following the first maximum is.A reached.V Thus,Y the maxima or minima, as the case maybeymay beused tot determine the vertical angle tothe aircraft; Bysuitably` calibrating the system the readings may be made directly in angles or, if fixed distances are` determinedin the direction ofthe aircraft, the calibration maybe made to read directly'the altitude ofthe craft. Y

lAccordingto a further feature of my invention, when the aircraft is located by observationof the proper maximum reading,` thisY position may be checked by moving the. antenna to ak higher position to locatie. thev corresponding null. This null will give. a sharper. direction indication than the maximum or lobe.

According to still further features" of' myinve'ntion, horizontal orf-vertical arrays may be used to sharpen the: directive indications; or a'A combination array incorporati'ngk both horizontal and vertical featuresmay used- In tliiscasethe array 2V should be. so mounted asto beV raised;- or lowered as aut-lit..` f l While I- have, described abovethe general prin*- ciplcs and. objects of my invention, a better understanding thereof may be had-,from .the following detailed description. tobc,rv read in; reference to the accompany-ing.drawings,y in which:

Fig'. 1 isa schematic illustration in perspective of one formv4 of appar-.aimsv byy which the method of this invention: may be. practiced;

Fig. 2 isaview in-.perspcctivel withparts broken away showingfanother form of anY antenna system of theinvention;

Fig. 3.is` a cha-rt diagram of thera'diation@ pat.- tern for the antenna system shown4 in Fig. l elevated; at about '7.14Lv wavelengths: above .the

ground;

Fig. fl is a chart., showing; acurvefindicating: the vertical angles of; echoreecting; obstructions: for a.p1urality of: vertical adjustments of the antenna;

Fig. 5. is a1.chart showing the-.radiation pattern for a horizontale loop; antenna;.

Fig. 6is a schematic'- illustration of. a horizontal antennaarrayfand Fig. '7' is a. schematic illustration of a: combina tion of horizontal and vertical antenna arrays.y

Referring; to.L Fig. l of` the'drawin'g's; a suitable mast lllv is shown supporting by means ofY pulleys lI-f,v I2 and lag, aline ll'to which radiant acting means such .as a.` dipoleI antenna f6" is attached. Thev line |:4 iswrap'ped inv grooves I`1 on a drum` |18 which lsprovided with a suitalfilepawlJ andratchet mechanism" anda handle 2! whereby the height or' the dipole It:h may be manually adjustedV and maintained. I'hefdruxn |'87 is provided with cal'ibrated portions l1d-jacent .the Y'grooves l'l" toind'icate the height at which the dipole niay bev at any particular position of thedrum.V To assist in reading the calibrations, an element 22' having a straightedgerdisposed` closely adjacent" the. 'drum maybe provided".l l

I To insure an effective; ground in the vicinity Yof the dipole fromA which' thet height of'` the dipole may be determined, rprovid'e a ground matwhic'h may'compri's'e ascie'eri mesh or. any other-.suitable mat construction atv the base ofN .the support-` IU. The mat' 24 may' be any desired. shape,` i. e. rec.- tangu'lar or. circulan. and extend horizontally abOuttlfieanteima-.QI a-v distance ot one or .two wavelengths.` Since horizontallyl polarized energy is used,r even. an impenfectly conducting` earth re ,iiectssubstantially all thefenergy strik-ingg'it at small'V angles so the mat; needw not be larzc.

The ground mat 24, however, may be omitted where the ground is satisfactory as a basis from which the height of the dipole may be measured.

The dipole I6 may be connected by a suitable transmission line 26 to a translator 28 associated with an indicator 30 which may be of the cathode ray type. 4Thetranslator may include a transmitter or a receiver or it may comprise, as shown in Fig. 2, both a transmitter and a receiver together with a suitable switching device whereby the antenna can be alternately used for transmission and reception. In this way, the same antenna may be used to transmit signals and to receive echoes for the purpose of determining the location of echo-producing obstructions.

Many antenna supporting arrangements and adjustable devices in addition to the form described above may be providedfor the purpose of carrying out my method of vertical angle scanning. In Fig. 2, for example, I show another form of adjustable support for an antenna system. Certainly positioned with respect to the mat 24, I show 'another form of adjustable support for an antenna, system. Centrally positioned with respect to the mat 24, I show a pole 32 anchored in the ground 34 and having slidable thereon a sleeve 35. Any suitable form of antenna or antenna array may be supported on the sleeve. For purposes of illustration I show the sleeve 35 provided with a vertical array of dipoles 33.

For vertical adjustment of the antenna, the sleeve may be connected at 36 to a line 31 riding over a pulley 38 at the upper end of the pole 32, the line extending downwardly therefrom axially of the pole to a pulley 3| adjacent the base of the pole and then laterally to a drum I8a. This drum may be calibrated and controlled by pawl and ratchet means similar to the drum construction shown in Fig. 1. The line 31, however, ex-

-tends in several turns about the drum with one end thereof secured to the drum at 39. A second line 46 is secured to the drum at 4| and after a few turns on the drum extends to the pole 32 for passage over a pulley 42 and then to the sleeve 35 to which it is connected at 4l). The line 46 may include a spring 44 to provide resilience to the line.

y The drum l8a may, however, comprise a narrow wheel with the lines 31 and 4D connected -together as a single line having a few turns about the wheel to provide a tight driving grip.

`If desired, a suitable chain and sprocket wheel .may be substituted for the drum and line.

Should either of these forms be used, a suit- `able counter or indicator with or Without reduction gearing, as the case vmay require, would then be desirable to determine the adjusted height of the antenna.

The dipoles 33 may be connected by a suitable vnetwork 50 to a switching device 52 whereby the antenna can be selectively connected electrically to a transmitter 54 and a receiver 55. The relceiver may have associated therewith a suitable scan a range of vertical angles and should air- 'craft be in the range of the locator, a reception will be made of the reflection of signals caused by the presence of the craft in such range even .though the craft be at a 'low' vertical angle.

It is known that when a horizontal dipole is placed a quarter wave above ground, maximum radiation occurs in the vertical direction.

The general expression for the radiation pattern F() at a vertical angle is given by the equation:

17(5) =sin (A sin where A is the height of the radiator above ground in electrical degrees. The maximum value of F08) may be taken as unity in computing the pattern.

The angle at which the maximum radiation takes place may be determined from the equation:

sin (e) =90 where n=the number of lobes.

At high spacings there may be a number of lobes but for the purpose of this invention the lowermost lobe is the one of interest. The angle for this lobe may be obtained by taking n to 1 in the above equation which then reduces to:

sin (6)- A90 From this it is clear that as the antenna is raised from the position at which one maximum in the vertical alone exists, that is a quarter wavelength above the earth, the vertical angle at which the maximum occurs becomes lower. At the height of a half wavelength, the pattern divides into two lobes, one for each quadrant above the axis of the abscissas. As the height is increased, the number of lobes increase in accordance with the number of wavelengths the antenna is raised above the ground. Consequently the angles should be read as the antenna is raised and the iirst maximum or the rst minimum used to determine the angle.

Referring to Fig. 3 of the drawings, I have shown a chart of the radiation pattern for the dipole shown in Fig. 1 raised to a height of about '7.14 wavelengths above the ground which places the lowest maximum atapproximately 2. The pattern has a large number of lobes as indicated in the quadrant shown in the chart. For seven wavelengths, there would be fourteen lobes in each quadrant above the axis of the abscissas as indicated, and as an additional wavelength is partially added to the height of the antenna, a ifteenth lobe will appear as indicated at 45. Should the height be increased to '7l/g wavelengths, the lobe 45 ywould split and add another lobe to the 14 lobes shown in the quadrant.

As is apparent from the chart in Fig. 3, the lobes decrease in width as they approach the horizontal. Thus for the lowermost lobe 46, the width is about two degrees when the dipole is at 7.14 wavelengths above ground. For radio location of aircraft or other obstructions at low vertical angles, I nd that by elevating the antenna and thereby causing the radiation lobes produced thereby to scan the space in vertical planes, an aircraft at a low vertical angle causing the reflection of signals is easily detectable by adjusting the elevational position of the antenna until the rst maximum indication is checked by moving the antenna to a higher posi- 'tion to locate the corresponding null. This null `will give a sharper direction indication but the -the positions of the radiation lobe characteristic at which the echo is vmost accurately detectable.

As hereinbefore stated, the indicating means 'of the system may be calibrated lfor fixed distances so that when the distance to an aircraft is .determined by reception of a signal reflected by the craft and the vertical angle of the crafts position is determined by scanning the space in accordance with my invention, the precise altitude of the aircraft may be directly determined.

From the chart shown in Fig. 4, it will be readily apparent that my scanning system is especially accurate at low angles of aircraft elevation. Thus, for any angle up to about -or 25 degrees, the degree of movement of the antenna is Substantial in proportion to the vertical angle scanned and may be easily calibrated. The calibration may in a-ddition be made quite accurately up to angles of about 45 degrees. Above 45 degrees the sensitivity of the system is so lowered that detection becomes approximate only. For lower angles, the relative movement of the antenna increases for a given angle of scanning thereby increasing substantially the degree of accuracy of my system for direction nding at the lower angles.

For devices providing adjustment to heights of approximately two wavelengths accurate measurements may be obtained between angles of about '7 to 45 degrees. Equipment having this limited adjustment is readily adaptable for portable use. For lower angles the antenna must be adjustable to greater heights, and such more elaborate equipment, of course, may be permanently installed.

In the place of the dipole, other forms of radiant acting means may be provided. In the chart shown in Fig. 5, I have indicated the radiation pattern for a horizontal loop antenna. The lower lobes of the pattern are long and narrow thereby providing sharp beam characteristics highly suitable for vertical scanning. For low vertical angle detection, the horizontal loop form of antenna when used in accordance with my invention gives for many purposes satisfactory results.

In Fig, 6, I show a horizontal array of dipoles spaced a half wavelength apart center to center. Each dipole is provided with a stub-line transformer whereby the three o-r more dipoles, as the case may be, may be matched for in phase operation. This array provides a radiation pattern having a beam appearance concentrated for sharpness in the horizontal. When the array is elevated in accordance with my invention, the radiation beam thereof increases further in sharpness for echo detection in the vertical angles at right angles to the array.

In Fig. 2 of the drawings, I show a vertical array of dipoles which is preferably operated out of phase to provide a concentrated pattern in the vertical. Each of the horizontal and vertical arrays of Figsl 6 and 2 respectively, may be used separately or theymay be used in combination as I have indicated in Fig. '7. When used in the combination form, the concentration .of the'pattern both in the horizontal and in the vertical provides an even more distinct :beam which, of course, is highly desirable for sharp echo direction determination. It is not always possible nor necessary to use the combination vertical and horizontal array and for many direction finding purposes, -t-he simpler Aforms of radiant acting means may be used.

From the foregoing, Vit is `clear that the vertical scanning feature of this invention is particularly adaptable to radio locator devices such as are used for locating the precise position of approaching aircraft. It is recognized that many variations in the Vconstruction of the antenna supporting means as well as in the vertical adjustment feature thereof and the association thereof with `calibrated `instrumentalities are Vpossible without departing 'from the invention. It is to be understood, therefore, that the forms herein shown and described are to be regarded as illustrative of the invention only and not as restricting the appended claims.

What I claim is:

l. The method of determining at a given location the vertical angle between the direction of an antenna system to an echo producing obstruction and the horizontal, comprising energizing said antenna system to produce a lobe of radiant energy having a known angular width, receiving on said antenna system reflected energy resulting from the reflection of said radiant energy from said obstruction, varying the height of said antenna system with respect to ground and indicating the variation in height of said antenna system which results when said received energy varies from a maximum to a minimum amount.

2. The method of determining at a given location the vertical angle between the direction of a radiant energy generating means to a reflecting object and the horizontal which comprises generating at said location a predetermined lobe of radiant energy, directing said lobe in the general direction of said object, receiving at said location reflected energy from said object, varying the height of the radiant energy generating means with respect to ground to cause said reflected energy to vary between a maximum and a mini.. mum value, and indicating the height of said generating means when said reflected energy has said maximum and minimum values,

3. In a radio locator responsive to echoes produced by obstructions the location of which is desired, an antenna system mounted at a height above ground to provide multiple radiation lobes in a vertical plane, means for varying` the height of said antenna system relative to ground to cause the radiation lobes produced thereby t0 sweep through a range of vertical angles, a transmitterl a receiver, means for alternately coupling the transmitter and receiver to the antenna system. means operatively associated with the receiver to indicate the intensity of the echo signal received, and means controlled by said height varying means to indicate the vertical angle of a radiation lobe characteristic at which the maximum reflection of signals from the obstruction is receivable.

4. In a radio locator responsive to echoes produced by obstructions the location of which is desired, an antenna system mounted at a height above gro-und to provide multiple radiation lobes in a vertical plane, means for varying the height of said antenna system relative to ground to cause the radiation lobes produced thereby to sweep 7 through a range of vertical angles, a transmitter, a receiver, means for alternately coupling the transmitter and receiver to the antenna system, and means controlled by said height Varying means to indicate the vertical angular position of a radiation lobe characteristic at which the echo of a transmitted signal is most accurately determinable.

ARMIG G. KANDOIAN.

REFERENCES CITED The following referencesy are of record in the file of this patent:

UNITED STATES PATENTSl Number Name Date 1,647,283 Esau Nov. 1, 1927 2,076,222 Bruce Apr. 6, 1937 2,157,159 Brown May 9, 1939 Number Number Name Date Hugon July 16, 1940 Hahnemann Sept. 3, 1940 Lyman Feb. 18, 1941 Kruesi Jan, 23, 1934 Rice Sept. 11, 1934 Moueix Oct. 17, 1939 FOREIGN PATENTS Country Date France Feb. 22, 1937 Great Britain Oct. 27, 1936 OTHER REFERENCES Bell Telephone System Technical Publication,

15 Monograph B-772, entitled Determination of the Direction of Arrival of Short Radio Waves, by H. T, Friis et a1., 1934. 

